Study of the Nitrogen Arc under Reduced Pressure

The paper presents a model of arc in a d.c. vortex plasma torch which allows to determine distributions of temperature and plasma electron density in conditions of reduced pressure. The model makes it possible to elucidate voltage-current characteristics of the arc at different pressures and its dynamic behaviour connected with the phenomenon of the electric arc root displacement. The experimental research also determined voltage-current characteristics for different flow rates and pressures. The fluctuations of the arc current and the arc voltage were measured. The corresponding wave shapes were analysed by Fast Fourier Transform. The frequency variations with flow rate, arc current and pressure were studied and discussed.     

Study of the feasibility of distributed cathodic arc as a plasma source for development of the technology for plasma separation of SNF and radioactive wastes

One of the key problems in the development of plasma separation technology is designing a plasma source which uses condensed spent nuclear fuel (SNF) or nuclear wastes as a raw material. This paper covers the experimental study of the evaporation and ionization of model materials (gadolinium, niobium oxide, and titanium oxide). For these purposes, a vacuum arc with a heated cathode on the studied material was initiated and its parameters in different regimes were studied. During the experiment, the cathode temperature, arc current, arc voltage, and plasma radiation spectra were measured, and also probe measurements were carried out. It was found that the increase in the cathode heating power leads to the decrease in the arc voltage (to 3 V). This fact makes it possible to reduce the electron energy and achieve singly ionized plasma with a high degree of ionization to fulfill one of the requirements for plasma separation of SNF. This finding is supported by the analysis of the plasma radiation spectrum and the results of the probe diagnostics.     

Soot Formation during the Decomposition of Chlorine-Containing Hydrocarbons with an AC Plasma Torch

Technical Physics - The process of decomposition of organochlorine compounds by a three-phase ac plasma torch with vortex arc stabilization is studied. The plasma torch had two zones for...     

Astigmatic telescopic transformation of a high-order optical vortex

Properties of an optical vortex light beam formed after the astigmatic telescopic transformation of a circular Laguerre-Gaussian mode are considered both theoretically and experimentally. The beam evolution is found to be in conformity with the general notions on the high-order optical vortex symmetry breakdown. Upon propagation, the asymmetric beam shows a sort of rotation of its transverse profile in accord with the energy circulation in the original circular mode; this process is described on the base of the beam intensity moments and the vortex and asymmetry components of its orbital angular momentum. An l-charged optical vortex converts into |l| secondary first-order vortices positioned on a straight line crossing the beam axis. Orientation of this straight line in the beam cross section and spatial separation of the secondary vortex cores depend on the propagation distance. Morphology (orientation and anisotropy) of all the secondary vortices is the same and depends on the propagation distance; the anisotropy can be characterized by the vortex component of the beam angular momentum. At certain distance, relative separation of secondary vortices with respect to the beam transverse size reaches its maximum that corresponds to the minimum anisotropy of the vortices. The results can be useful in the context of current research of the optical vortex arrays.     

Processes and properties of electric arc stabilized by water vortex

Experimental investigation of an electric arc stabilized by a water vortex was carried out in a DC arc plasma torch for the power range 90-200 kW. Volt-ampere characteristics of the arc as well as the power balance were determined separately for the part of the arc column stabilized by water and for the remaining part between the nozzle exit and the external anode. The temperature of arc plasma close to the nozzle exit was determined by emission spectroscopy. Negatively biased electric probes in the ion collecting regime were used for determination of the plasma flow velocity. The measured temperatures up to 27000 K, and velocities up to 7 km/s are higher than the values commonly reported for plasma torches with DC arcs stabilized by a gas flow. Mass and energy balances within the arc chamber were determined from the experimental results. The radial transport of the energy by radiation was identified as a decisive process controlling the arc and plasma properties. The balance of radial energy transport was studied. The ratio of energy spent for evaporation of the water to the energy absorbed in the evaporated mass is very low in the water stabilized arc. This is the principal cause of high plasma temperatures and velocities found by the measurements     

不同水深水下湿法焊接电弧等离子体数密度研究

水下湿法焊接技术应用日益广泛,由于特殊的焊接条件,导致深水下其焊接质量亟待改善。通过搭建水下湿法焊接实验平台,压力罐调节气压分别模拟0.3, 20和40 m水深,界定焊接引弧阶段,分别采集三个水深环境条件下焊接引弧阶段的光谱信息及电压电流数据,采集光谱信息时利用光谱仪的延时触发功能,分别采集引弧5,10,15,20和25 ms时刻的光谱数据,对采集到的电弧光谱数据整理后进行诊断分析。诊断分析时结合NIST原子光谱数据库以及特征谱线的相关数据,得到各元素粒子的识别结果。对于高价态的元素离子态,因为其电离能比较大,激发电离程度会受到电弧温度变化的影响,不能仅靠光谱图进行识别诊断,还需要进一步对其组分进行数密度计算。结合水下湿法焊接电弧光谱诊断的信息和水下湿法焊接反应过程,确定出计算中要考虑的电弧等离子组分的18种粒子,求解由沙哈方程、解离电离方程、准中性方程、气体压力平衡方程等组成的方程组,采用牛顿迭代法对方程组进行联立求解,对于求解非线性方程组,采取分段赋值的方法,得到等离子体组分在三个水深环境下的数密度,并对其变化规律进行分析,探究不同水深环境对焊接电弧等离子体数密度影响及因素。研究表明各个粒子数密度在不同水深条件下的变化是非线性的,随着水深加大电弧数密度变化幅度也快速增大。随着水深的增加,电弧会受到压缩,但电弧不能无限制被压缩;粒子的电离受温度的影响,温度越大电离作用越强烈,但当温度升高到一定程度时,各个电离作用有其电离极限,粒子数密度也不会无限增大。通过不同水深条件下焊接电弧引弧阶段数密度的计算,对水下焊接电弧引弧阶段粒子产生的机理进行了研究,为提高水下焊接电弧稳定性及电弧模拟仿真计算等提供了理论依据。     

Preliminary investigation of arc stabilization with a forced vortex

The stabilization of an arc using a forced vortex was studied experimentally. Measurements on the arc characteristics were made as a function of the stabilizing flow parameters. It was found that the behaviour of the arc may be understood in terms of measurements made on the stabilizing flow without the arc. It is concluded that stable arc operation may be achieved using forced vortex stabilization, but that in open-ended systems end effects on the vortex are likely to cause severe convective losses in the arc.     

Effect of gun current on the microstructure and crystallinity of plasma sprayed hydroxyapatite coatings

Hydroxyapatite (HA) is a bioactive material because its chemical structure is close to the natural bone. Its bioactive properties make it attractive material in biomedical applications. Gas tunnel type plasma spraying (GTPS) technique was employed in the present study to deposit HA coatings on SUS 304 stainless steel substrate. GTPS is composed of two plasma sources: gun which produces internal low power plasma (1.3-8 kW) and vortex which produces the main plasma with high power level (10-40 kW). Controlling the spraying parameters is the key role for spraying high crystalline HA coatings on the metallic implants. In this study, the arc gun current was changed while the vortex arc current was kept constant at 450 A during the spraying process of HA coatings. The objective of this study is to investigate the influence of gun current on the microstructure, phase crystallinity and hardness properties of HA coatings. The surface morphology and microstructure of as-sprayed coatings were examined by scanning electron microscope. The phase structure of HA coatings was investigated by X-ray diffraction analysis. HA coatings sprayed at high gun current (100 A) are dense, and have high hardness. The crystallinity of HA coatings was decreased with the increasing in the gun current. On the other hand, the hardness was slightly decreased and the coatings suffer from some porosity at gun currents 0, 30 and 50 A.     

外磁场作用下的磁等离子体动力学过程仿真

磁等离子体动力学推力器是空间高功率电推进装置的典型代表,磁等离子体动力学过程是其核心工作机制.为深入理解外磁场对其工作特性的影响,本文采用粒子云(particle in cell,PIC)方法结合基于自相似准则的缩比模型,进行外加磁场作用下磁等离子体动力学推力器工作过程的建模仿真,通过与实验结果对比验证模型和方法的可靠性,并重点分析推力器点火启动过程的等离子特性参数分布,以及外磁场和阴极电流对推力器工作性能的影响.研究结果表明:阴阳极放电电弧构建是推力器启动和高效工作的关键步骤;外磁场强度较低工况不利于构建稳定放电电弧,等离子体束流集中于轴线附近,推力主要产生机制是自身场加速;外磁场强度较高时,阴阳极放电电弧稳定,推力产生主要机制是涡旋加速,推力、比冲随外磁场强度线性增大;推力器效率随阴极电流和外磁场强度增大而增大;放电电压随阴极电流增大而增大,但随外磁场强度的增大表现出先减小后增大的趋势.     

外磁场作用下的磁等离子体动力学过程仿真

磁等离子体动力学推力器是空间高功率电推进装置的典型代表,磁等离子体动力学过程是其核心工作机制.为深入理解外磁场对其工作特性的影响,本文采用粒子云(particle in cell,PIC)方法结合基于自相似准则的缩比模型,进行外加磁场作用下磁等离子体动力学推力器工作过程的建模仿真,通过与实验结果对比验证模型和方法的可靠性,并重点分析推力器点火启动过程的等离子特性参数分布,以及外磁场和阴极电流对推力器工作性能的影响.研究结果表明:阴阳极放电电弧构建是推力器启动和高效工作的关键步骤;外磁场强度较低工况不利于构建稳定放电电弧,等离子体束流集中于轴线附近,推力主要产生机制是自身场加速;外磁场强度较高时,阴阳极放电电弧稳定,推力产生主要机制是涡旋加速,推力、比冲随外磁场强度线性增大;推力器效率随阴极电流和外磁场强度增大而增大;放电电压随阴极电流增大而增大,但随外磁场强度的增大表现出先减小后增大的趋势.     

Production of long,laminar plasma jets at atmospheric pressure with multiple cathodes

Plasma jets from conventional non‐transferred arc plasma devices are usually operated in turbulent flows at atmospheric pressure. In this paper, a novel non‐transferred arc plasma device with multiple cathodes is introduced to produce long, laminar plasma jets at atmospheric pressure. A pure helium atmosphere is used to produce a laminar plasma jet with a maximum length of >60 cm. The influence of gas components, arc currents, anode nozzle diameter, and gas flow rate on the jet characteristics is experimentally studied. The results reveal that the length of the plasma jet increases with increasing helium content and arc current but decreases with increasing nozzle diameter. As the gas flow rate increases, the length of the plasma jet initially increases and then decreases. Accordingly, the plasma jet is transformed from a laminar state to a transitional state and finally to a turbulent state. Furthermore, the anode arc root behaviours corresponding to different plasma jet flows are studied. In conclusion, the multiple stationary arc roots that exist on the anode just inside the nozzle entrance are favourable for the generation of a laminar plasma jet in this device.     

基于光谱诊断的热源间距对激光-脉冲GMAW复合焊等离子体物理特性影响研究

激光电弧复合焊中,热源间距会影响到等离子体物理特性,进而影响到焊接过程的稳定性及焊接质量。 基于Boltzmann作图法和Stark展宽法研究了不同热源间距下的激光-脉冲GMAW复合焊峰值阶段的温度场和电子密度分布,并结合高速摄影手段分析了热源间距对温度和电子密度的影响规律。 光谱诊断结果表明,随着热源间距的增大,激光等离子体的温度和电子密度都没有明显的变化;电弧温度出现下降,电弧电子密度则呈现先增高后降低的趋势。     

Influence of retardation between orthogonal components of circularly polarized light in the vortex phase plate on the structure of diffracted beam

The influence of retardation between orthogonal components of circularly polarized light on diffraction pattern generated by the vortex phase plate with a birefringence medium is considered. It is shown that if the ideal retardation π is broken, the pattern diffracted from the phase plate is described by superposition of two components: the vortex beam with the deep hole and the incident beam which preserves its initial characteristics. The computation results characterizing the influence of retardation on the Gaussian and Airy beams transformation in the vortex phase plate are presented. These results point out that vortex beam characteristics are very sensitive to retardation shift from its ideal value. We analyze and present the characteristics of the vortex phase plate that are required for the true vortex pattern generation.     

激波/边界层干扰对等离子体合成射流的响应特性

利用高速纹影系统和数值模拟方法研究了激波/边界层干扰对逆流喷射的等离子体合成射流的响应特性,并揭示了流动控制机理.实验在来流马赫数Ma=3.1的风洞中进行,测试模型采用钝头体和压缩斜坡的组合模型,等离子体合成射流激励器安装在钝头体头部.纹影系统捕捉了放电频率为f=1 kHz和f=3 kHz的激励对附体激波形态和分离激波运动的控制效果.等离子体合成射流使压缩斜坡激波/边界层干扰区域的起始点向下游移动,分离泡尺寸减小,附体激波强度减弱,发生弯曲,再附点移向上游,与此同时分离激波向附体激波逼近.与f=3 kHz激励相比,f=1 kHz激励的射流流量更大,对激波/边界层干扰的影响范围更广、控制效果更好.通过数值模拟,揭示了射流与来流相互作用对下游流场的作用机理:射流与来流相互作用诱导出大尺度旋涡,大尺度旋涡耗散发展增强了近壁面流场的湍流度;压缩斜坡上游近壁面的流场性质发生变化,进而导致了压缩斜坡激波/边界层干扰区域流动的变化.     

The characteristics of surface arc plasma and its control effect on supersonic flow

The characteristic of surface arc plasma included millisecond and microsecond actuation in supersonic flow is investigated both experimentally and numerically. In the experiment, the discharge characteristic of surface arc plasma in quiescent air and supersonic flow is recorded. The stable oblique shock could be observed with millisecond actuation. And the unstable compressive wave could be also observed with microsecond actuation. In the numerical investigation, plasma actuation is defined as a source term with input power density from discharge V–I characteristic, which is expected to better describe the influence of heating process. The numerical results are coincident with experimental results. In order to confirm the capability of surface arc plasma actuation to control supersonic flow, experimental investigations on control shock induced by ramp and separation of boundary layer induced by impinging shock are performed. All the results demonstrate the control effect of surface arc plasma actuation onto supersonic flow.     

GC-MS分析川赤芍挥发油成分

采用水蒸气蒸馏法从川赤芍中提取挥发油,用气相色谱/质谱联用法（GC/MS）检测并分析其化学成分,用归一化法测定其相对含量,结果鉴定出37个成分,占挥发油总成分的86.15％.主要成分为苯甲酸、牡丹酚和邻甲基苯酚.     

Methods of stabilizing the arc discharge in the spectral analysis of powdered materials

Two ways of introducing powders into the gas cloud of an arc are suggested. The techniques were developed in order to eliminate fractional vaporization of specimen components and to obviate the effect of chemical composition on the results of spectral analysis of powdered materials. The entry of specimen components into the plasma and the effect of chemical composition on arc discharge conditions (primarily the plasma temperature) were studied. The drawbacks and advantages of existing methods of introduceing powdered specimens into the arc are discussed. The relative intensity of pairs of spark and arc spectral lines of iron was calibrated with respect to temperature in order to permit measurement of the temperature characterizing the excitation conditions.     

Explosive plasma-vortex optical radiation sources

The results of experimental study of explosive radiation sources based on pulsed injection of a cumulative plasma jet into atmospheric air are considered. The injection process is accompanied with intense vortex formation as well as the formation of a large-scale toroidal plasma vortex. High-power electromagnetic radiation in the optical range is generated due to shock-wave processes during deceleration of a plasma jet in air and plasma-chemical processes in the vortex. The temporal structure of a radiation pulse being generated contains components from the micro- and millisecond range. For a 20-g mass of the explosive charge, a peak radiation power of 300 kW/sr and an energy yield of 400–600 J/sr integrated over the emission spectrum are attained. The efficiency of conversion of the chemical energy of the explosive into radiation is 5.0–7.5%.     

Vortex of Fluid Field as Viewed from Curvature

The vortex is a common phenomenon in fluid field. In this paper, vortex can be represented by curvature c, which varies with arc length s. The variance of point (x,y) with arc length in stream line satisfies a 2-order variable-coefficient linear ordinary differential equation. The type vortex can be analyzed qualitatively by this ordinary differential equation.     

基于Kriging代理模型的DBD等离子体控制叶顶泄漏流动研究

本文采用数值方法研究了布置于涡轮动叶叶顶的多个等离子体激励器组合对间隙泄漏流动的影响。结果表明:不同的极板数目和位置组合对间隙泄漏流量有着十分明显的影响。在叶顶沿吸力边布置等离子体激励器的最佳位置在大约55%S/Sps处,布置相同数目的等离子体激励器,在靠近尾缘处的控制效果要远好于在前缘附近的控制效果;等离子体激励器在叶顶靠近吸力边处产生诱导涡,阻碍了间隙内流体的流动,使泄漏流体的速度降低。同时还会使得分离泡的破碎提前,有利于减小掺混损失;对泄漏流动的控制效果不会随着等离子体极板数增加而持续增强,而存在一定限度,最优布置方式的泄漏流量较原型下降约46%,相应的出口截面能量损失下降了15.7%。